Method and system for providing a video signal

ABSTRACT

In accordance with the specific embodiment of the present invention, a tuner alternates between receiving a 
     first video signal and a second video signal, such that every other frame of a specific signal is received. This is accomplished by writing to an IF1 and IF2 control register, during a vertical blanking interval. Subsequently, the video images are displayed in full motion video by interpolating the alternating frames of data not received by the tuner.

FIELD OF THE INVENTION

The present invention relates generally to providing video signals, andmore specifically to providing multiple video signals using a singletuner.

BACKGROUND OF THE INVENTION

The use of multiple tuners in video applications to provide suchfunctions as picture in a picture (PIP) is well known. By providing suchcapabilities, it is possible for a user to monitor multiple channelssimultaneously.

In order to display simultaneous full motion video images, playbackdevices, such as televisions, have to incorporate multiple tuners. Themultiple tuners may be incorporated within an individual playbackdevice, or may be in external devices, such as video cassette recorder,whereby the external device provides the a received signal the playbackdevice.

The use of multiple tuners within a television increases the overallcost of a system. Cabling and associated connectors increase the cost ofsystems where an external tuner is used to provide a received signal toa television to provide the second full motion video image. The use ofan external tuner further requires the use of multiple control devices,such as remote controls, to control each of the tuning devices. Multipletuners within a television inherently increase the cost of the system.The increased complexity of such systems is disadvantageous. Therefore,a method and system for overcoming the disadvantages of the prior artsystems would be advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates, in block diagram form, a system in accordance withthe present invention;

FIG. 2 illustrates, in block diagram form, the tuner of FIG. 1 ingreater detail;

FIG. 3 illustrates, in time line form, when fields of video data aretransmitted;

FIG. 4 illustrates, in graphical form, a composite video signal;

FIG. 5 illustrates, in block diagram form, an alternative implementationof the tuner of FIG. 1;

FIG. 6 illustrates, in block diagram form, an alternative implementationof the tuner of FIG. 1; and

FIGS. 7 and 8 illustrate, in flow diagram form, specific implementationsof the method of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In accordance with a specific embodiment of the present invention, atuner alternates between receiving a first video signal and a secondvideo signal, such that every other frame or field of video data isreceived for each specific signal. The signals are alternativelyreceived by providing alternating data values in each of an IF1 and IF2control register. The values are switched during the vertical blankinginterval of the received data. Subsequently, the video images aredisplayed in full motion video by interpolating the missing fields ofdata not received by the tuner.

The present invention is best understood with reference to the figures.FIG. 1 illustrates a block diagram of a system in accordance with thepresent invention. FIG. 1 includes an antennae 105 connected to a tuner110. The tuner 110 is connected to an analog-to-digital converter 112.The analog-to-digital converter 112 is connected to the video decoder114. The video decoder 114 is connected to the memory 116. Memory 116 isconnected to display engine 118. The display engine 118 is connected tothe display device 120.

In operation, the tuner 110 receives a signal from antennae 105.Generally, the signal received from antennae 105 would be understood toinclude composite signals of the type associated traditionallytransmitted video signals. However, it would be understood that theantennae 105 can also represent signals received in a compressed oruncompressed form, from other media, including the internet, and othertransmission media whereby multiple signals are transmitted at variousfrequencies.

The tuner 110 selects one of the plurality of received signals basedupon information received across the bus 130. By receiving a pluralityof information across the bus 130, it is possible for the tuner 110 toswitch between a plurality of frequencies, thereby allowing the tuner110 to provide the information necessary to display a plurality of videoimages on the display device 120. The information provided by the tuner110 is provided to the analog to digital converter 112. Theanalog-to-digital converter 112 converts the received analog signalsinto a digital format. The converted digital information is provided tothe video decoder 114.

The video decoder 114 decodes the digital information from it retrievedformat into a digital data of a chosen protocol. Such protocols includesuch as a YUV color space protocol, or an RGB color space protocol. Thedecoded information generated by the video decoder 114 is stored via bus140 in memory 116. Note that additional processing of the decoded signalcan occur between the actual decoding of the data and its storage in thememory 116.

Once stored in memory 116, the display engine 118 accesses the memory116 to retrieve the stored image and provide it to the display device120. As discussed previously, with reference to the tuner 110, datarepresenting multiple images is being received by the tuner 110, whichrepresent a single tuner. The received information is stored in separatelocations within the memory 116.

In a specific implementation, where the tuner 110 is alternativelyreceiving fields of data on multiple channels, it is be necessary forthe video decoder, or some other portion of the system, to interpolatethe missing image data. For example, where the tuner 110 alternatesreceiving fields from a first frequency (associated with a firstchannel) and a second frequency (associated with a second channel), onlyevery other field of a given channel will be provided by the tuner 110.Therefore, it is necessary for the video decoder, or some other portionof the graphics adapter, to interpolate the missing image data basedupon the received data alternating received fields. Examples of suchtechniques, which are well know, and include vertical filtration.

Fields associated with a plurality of full motion video channels arestored in memory 116 for retrieval by the display engine 118. Whendisplayed upon the display device 120, multiple channels of video can beviewed. Generally, the multiple channels are displayed in separatewindows where a computer monitor is being used.

FIG. 2 illustrates in block diagram form a portion of the tuner 110 inaccordance with the present invention. Specifically, the portion of thetuner illustrated in FIG. 2 includes mixers 212 and 216, a band-passfilter 214 for performing band-pass filtering, a control portion 217,and a tuning portion 230.

In operation, the signal received from antennae 105 is combined at mixer212 with a frequency provided by the tuning block 230. The output signalof the mixer 212 is provided to the filter block 214. The band-passfilter 214 will provide a selected channel frequency. By appropriatelyfiltering the received signal, a specific portion of the received signalcan be further processed. The filtered signal from band-pass filter 214is provided to mixer 216, which receives a frequency from the tuningblock 230. The output of the mixer 216 provides a desired IF frequency.Note the frequencies provided by the tuning block 230 determine theactual channel frequency selected. The output if mixer 216 is receivedby control portion 217, which provides various control functions to thetuning portion 230.

The tuning portion 230 comprises a frequency generation block 218containing multiple frequency generators. Each of the frequencygenerators of portion 218 receive a frequency value. The frequencyvalues are stored in registers 220 and 222 for specifying the IF1 andIF2 frequency values respectively.

FIG. 3 is a time line indicating the sequence during which individualfields are received by the antenna 105. Video images include a pluralityof sequential fields. By displaying the plurality of sequential framesat an appropriate rate a full motion video image is produced. Note thatthe channel value X is a function of the IF1 and IF2 frequency values.By providing specific IF1 and IF2 frequencies, a specific channel X canbe selected.

Each frame is transmitted as two fields. Separate fields are utilized inorder to improve video quality by accommodating the interlacing ofimages. Therefore, referring to FIG. 3, F1A and F1B represent two fields(A and B) associated with the frame 1 (F1) of channel X. Likewise, F2A,and F2B represent the two fields associated with a frame 2 of channel X.

FIG. 4 illustrates a the vertical blanking interval associated with anNTSC composite video format. Time periods 1–3 represent the final threefields associated with a particular frame. Time periods 4–24 representthe vertical blanking interval (VBI), which includes variousequalization and serration pulses (not specifically illustrated). Thevertical blanking interval, in FIG. 4 is of specific interest because ina specific implementation of the present invention the tuner is changedduring the VBI interval.

Referring back to FIG. 2 and assuming two channels are to be provided bythe tuner 110, the IF1 control register and IF2 control register areloaded with the appropriate IF1 and IF2 values to tune into a firstselected channel. In a specific embodiment, the values contained withinIF1 control register and IF2 control register will be changed at afrequency allowing for adjacent fields of different channels to bereceived. In other words, referring to FIG. 3, the active video of afirst channel will be received during time T1, and the active video fora second channel will be received during time T2

In order to accomplish receiving adjacent fields, one set of controlregister values would be stored in order to receive a first channel, andjust prior to the second time, a second set of IF1 and IF2 controlregister values will be stored within the registers 220 and 222 in orderto receive the field FIB associated with a second channel. In analternating manner, the value stored within the control registers IF1and IF2 are be changed in order to receive alternating field from eachof the first and second frequency.

In an alternate embodiment, it would be understood that instead ofreceiving alternating fields, it would be possible to receivealternating frames. In this manner, when tuned to a first frequency, thefields F1A and F1B would be received by the tuner 110. Subsequently, thevalues associated with the control registers of IF1 and IF2 would beupdated to reflect the second channel whereby the field F2A and fieldF2B of the second frame for the second channel would be received.

In addition, it is understood by one skilled in the art that in additionto receiving adjacent fields associated with a single frame, such asfrom T1 to T3, it would be possible to receive adjacent fieldsassociated with different frames. In other words, frame F1B and F2Acould be received for a single channel in an alternating manner. Aspreviously discussed, interpolation techniques can be used in order tofill in the missing data in order to accommodate the display of fullmotion video.

In order to accommodate the rapid tuning from one channel to another, afast tuner, such as a solid state tuner, should be used. However, thesolid state tuners available support a slow bus interface protocols overthe bus 130, see FIG. 1, to set the values of IF1 register and the IF2register. Therefore, either a faster bus interface over the bus 130needs to be used, or alternate techniques within the tuner 110 need tobe used in order to support the rapid switching between channels.

In one implementation, the bus interface 130 of FIG. 1 is a businterface capable of supporting high speed transfers of data directly tothe IF1 and IF2 control registers 220 and 222. Currently, the bus 130 isan I²C bus interfaces, which is too slow to accomplish the presentinvention by directly writing to the register. Therefore, otherproprietary or standard bus interfaces protocols capable of changingdata fast enough to allow tuning into multiple channel would need to beused. Such a bus would have approximately 1.2 milliseconds to write thedata and acquire locking. While possible with very fast three wirebusses, or other multiple data bit protocols, such high rates may beimpractical.

FIG. 5 illustrates another implementation of the tuning block 230 ofFIG. 2 in accordance with the present invention. FIG. 5 allows for anIF1 prelude register, and an IF2 preload register to allow for rapidchange of the IF values of the actual control registers 220 and 222. Inthis implementation, the traditional I²C bus protocol, or virtually anyother bus protocol, can be used to load data into the IF1 and IF2prelude register at any time. Once the vertical blanking interrupt asignal is detected, or other desired event, a load signal is generatedin order to rapidly load the value stored preload values into the IF1and IF2 control registers 220 and 222 respectively. Once loaded, thefrequency generator 118 will generate and provide new frequencies to themixers 112 and 116 of FIG. 2. Noted that detection of the verticalblanking interrupts signal can be accomplished through the controlportion 117 of FIG. 2 which in turn would provide the load signal to theIF1 and IF2 control registers of FIG. 5. One advantage of theimplementation of FIG. 5, is that it allows for the traditional I²Cinterface to be used since the new channel can be loaded over a longerperiod of time.

FIG. 6 illustrates another implementation in accordance with the presentinvention. In FIG. 6, there is a set of channel 1 control registers 610and a set of channel 2 control registers 620. Each of the register sets610 and 620 include an IF1 register as well as an IF2 register. The IF1registers of both channel 1 and channel 2 are provided to a multiplexor630. Likewise, the IF2 registers of channel 1 and channel 2 are providedto a multiplexor 631. A common channel select signal is received by eachof the multiplexors 630 and 631. When in a first state, the channel 1controller register values are provided to the frequency generator 618.When the channel select is in a second state, the channel 2 controlregister values are provided to the frequency generator 618. In thismanner, it is possible to load the channel 1 and channel 2 controlregisters 610 and 620 with data, and other control information, in orderto provide for rapid switching between selected channels. As previouslydiscussed, the control portion 117 can used in order to monitor thereceived signals to determine when a vertical blanking interrupt, orother appropriate signal event, occurs to switch between the selectedchannels.

FIG. 7 illustrates a method in accordance with the present invention. Atstep 701, the receiver is tuned to a first frequency. As discussedpreviously, this is accomplished by providing an IF1 control registervalue, and an IF2 control register value. Based upon the IF1 and IF2control registers values, a specific channel of video can be received bythe tuner.

At step 702, a first field of video associated with the first frequencyis received. As discussed with reference to FIG. 3, a field of video isdescribed to be at least a portion of a frame of video. Whereby a frameof video represents an entire screen of information.

At step 703, the receiver is tuned to a second frequency. In a specificimplementation, this occurs during the vertical blanking interval of thecomposite signal. When provided during the vertical blanking interval,the step of providing needs to occur in less than approximately 1.2milliseconds. During this time period Phase Locked Loop settling shouldoccur.

At step 704, a second field of video associated with the secondfrequency is received. The first frame of video and the second frame ofvideo are adjacent in time. Referring to FIG. 3, adjacent in time forfields of different frequencies means receiving a first field of videoduring time T1 for a first frequency, and a field at time T2 for asecond frequency.

At step 705 the first field of video is displayed. It should be noted,that the first field of video may actually include interpolated datafrom previously or subsequently received frames or fields of data.

At step 706, the receiver is tuned to the first frequency after the stepof receiving the second field.

At step 707, a third field associated with the first frequency isreceived.

At step 708, the third field is displayed, wherein the first field andthe third field are associated with adjacent frames of a common videoimage. Referring to FIG. 3, adjacent video image fields would includeF1A and F2A. In other words, the first frame would include fieldstransmitted from time T1 through time T2, while the second adjacentframe associated with full motion video would include fields transmittedfrom time T3 through time T4.

At step 709, the second field, is displayed in an area of the displaydevice that is substantially mutually exclusive from the first image. Inother words, the second image is displayed in a separate window, or aseparate portion of the screen from the first image, such that the firstimage and the second image can be displayed simultaneously on a singledisplay device, or on multiple display devices simultaneously.

The present invention provides an advantage over the prior art in thatit allows for multiple video signals to be received using a singletuner. The multiple images can be displayed simultaneously on a singledevice, such as in a picture in a picture format, or on separate displaydevices. Being able to control a tuner that can receive multiple imagessimultaneously is an advantage over the prior art, in that it reducesthe need for a second tuner whether associated with the television, orwith an associated video cassette recorder as discussed previously. Oneof ordinary skill in the art will understand that variousimplementations of the present invention can implemented withoutdeparting from the scope of the claimed invention herein.

1. A method for tuning a system comprising: tuning a video tuner to afirst frequency; receiving a first field of video on the firstfrequency; interpolating missing image data for the received firstfield; after a video blanking interval is detected in a video signal onthe first frequency, tuning the video tuner to a second frequency;displaying the first field of video with interpolated missing image dataon a display device; receiving a first field of video on the secondfrequency; interpolating missing image data for the received first fieldon the second frequency; after a video blanking interval is detected ina video signal on the second frequency, retuning the video tuner to thefirst frequency; and displaying the second field of video with theinterpolated missing image data on the display device.
 2. The method ofclaim 1 further comprising: providing a second frequency indicator tothe video tuner prior to the step of tuning the video tuner to a secondfrequency.
 3. The method of claim 2, wherein the step of providingincludes providing the second frequency indicator in less thanapproximately 1.2 milliseconds.
 4. The method of claim 1 whereininterpolating missing image data for each of the received first field onthe first frequency and the first field on the second frequency,includes interpolating data based on previously or subsequently receivedfields of data.